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Vaccine Acceptance Still an Issue

by Steven Novella, Dec 05 2011

Perhaps the weak link in the effectiveness of vaccines is public acceptance. Individual vaccine types vary in terms of their effectiveness, but all are reasonably effective and very safe. Vaccines are, in my opinion, one of the “home runs” of modern medicine – scientists hit upon a way to marshal our own immune systems to make us resistant or even completely immune to certain infectious diseases. The result has been a dramatic decrease in diseases that used to plague humanity, and the complete eradication of one (smallpox).

It is ironic that the greatest barrier to the effectiveness of the vaccine program is public acceptance. Part of the problem is that very high acceptance is needed in order to achieve what is called “herd immunity” – where there is sufficient protection in the population that an infected individual will likely not cause an outbreak.

In the US the numbers are pretty good, and have remained so even through the recent increase in the anti-vaccine movement. About 68% of children complete the full routine vaccination series. Many of the individual vaccines have compliance rates in the 90s (MMR, for example, was 92.1% in 2008). The level required for herd immunity varies, but it is generally around 85-90%.

Acceptance of the flu vaccine in the US is much lower. Last year the cumulative flu vaccine use in the >6 month old population was 43%. Many people feel that the flu vaccine is not necessary, that it doesn’t work, or even that it is not safe. Uptake is slowly increasing – we  are at slightly higher levels this year compared to last year, but there is still a long way to go. The flu vaccine does have the added challenge of matching the strains covered in the vaccine to the circulating strains, so efficacy does vary from year to year, averaging about 50% effective. This year, so far, it seems that the match is a good one. We are nowhere near herd immunity levels with the flu vaccine.

Increasingly parents are opting for alternative vaccine schedule – 13% according to a recent survey.  And yet, there is no evidence that any of these alternate schedules is any safer than the standard schedule, but they are less effective – they leave children vulnerable for longer to vaccine-preventable diseases. Use of an alternate vaccine schedule, in my opinion, represents a fundamental mistrust of the medical system. The vaccine schedule is not arbitrary. It is based upon a careful review of evidence, matching the timing of each vaccine to when it is needed and when the child’s immune system is mature enough to handle it. The need for booster shots is determined by measuring antibody levels in response to vaccination. All this evidence is reviewed by panels of experts to determine the optimal schedule.

In place of this system 13% of parents would rather substitute either their own judgment or “Dr. Bob’s Alternative Vaccine Schedule.” They apparently buy into the notion that some lone maverick is better able to parse the research than panels of experts.

The historical relationship between vaccine implementation and the reduction of specific infectious diseases is very clear (which does not stop the anti-vaccinationists from denying it). Further, as pockets of vaccine denial are becoming more common, so is the recurrence of vaccine-preventable diseases. Right now Europe is in the midst of a measles outbreak, with more than 26,000 cases, 9 deaths, and 7,288 hospitalizations so far this year. MMR (measles, mumps, rubella) vaccine uptake is lower in Europe than the US. They are also dealing with many immigrant populations with lower levels of vaccine use, so it’s not all vaccine refusal.

This raises another issue with vaccine use – they are very cost effective. In case you haven’t noticed, we are in the middle of a growing health care cost crisis. The cost of health care is a complex issue I cannot get into here – but what is clear is that vaccines are extremely cost effective. In some cases they may even be cost saving – the cost of vaccine is lower than the health costs of hospitalizations they prevent.

Outbreaks of vaccine-preventable diseases are also occurring in the US. Recently there has been an outbreak of whooping cough on Long Island, for example. Whooping cough is a potentially serious illness, especially in infants. Infants are vulnerable until they are old enough to get the vaccine themselves and so depend upon herd immunity.

Often anti-vaxers point out that when such outbreaks occur it is common for most infected individuals to be among the vaccinated. They imply that vaccines therefore do not work. This is also the case with the whooping cough outbreak. This is an abuse of statistics, however.

What is important is the risk of getting the disease in the vaccinated vs unvaccinated populations. With > 90% of the population getting the vaccine the vaccinated population is much larger than the unvaccinated population. Being vaccinated greatly reduces the risk of getting the disease. Also, if someone gets the disease despite being vaccinated they are likely to have a much milder course.

It also should be noted that while overall vaccine rates are high, there are pockets of low compliance (and these are locations where outbreaks are sometimes occurring).

Anti-vaxers often cite the parents’ right to “informed consent” concerning vaccines. I agree – parents should be fully aware of the risks and benefits of vaccines. When informed with accurate information (as opposed to the misinformation from anti-vaxers) the decision to vaccinate should be an easy one.

38 Responses to “Vaccine Acceptance Still an Issue”

  1. Wrong says:

    Just a heads up Dr Novella,
    “Begin vaccinated greatly reduces the risk of getting the disease. Also, if someone gets the disease despite being vaccinated they are likely to have a much milder course.”
    I think the word processor did something funny, and what’s put at begin is meant to be being. I hope you don’t mind the correction.

    A great article, especially the mention of the statistics abuse by anti-vaxxers, and the mention of what amount of vaccination is required for herd immunity was very informative.

  2. Wesley Goodford says:

    I don’t see why the consent of the parents should be required. We no longer consider children the personal property of the parents any more, and in some cases children need to be protected from their parents.
    We no longer allow the pater familias to kill his children for disobedience, or even (as was the norm where I live just a generation a go) to whip them. Nor do we allow parents to force their sons to skip school for work, or to sell their daughters into sexual slavery to pay of debts.
    The idea that parents own their children’s lives is antiquated and repugnant. When parents refuse to get their children vaccinated we should temporarily remove the children from their care, vaccinate them, and possibly investigate the family to check for other forms of child abuse.

  3. Other Paul says:

    The result has been a dramatic decrease in diseases that used to plague humanity, and the complete eradication of one (small pox).

    Given the rather low number of generations of humanity that have been around since the beginning of vaccination, I suppose it’s unreasonable to expect more. But I’ve always found this figure rather disappointing. Is it just me, am I exceptionally hard to please?

    • Wesley Goodford says:

      Complete eradication is hard. Often diseases are endemic in hard to reach areas, vaccines expensive and often religious groups agitate against them. (An example would be the Islamic polio vaccine fatwa in Nigeria.) And even when you’re successful it can take decades before the last single cases disappear.

  4. CountryGirl says:

    If you have ever been in the same house with a baby with whooping cough then you can understand the seriousness of this disease. When I was a child in the 40’s and 50’s the fear of polio was palpable especially since my mother had polio as a child and my uncle died from it. For the majority of parents in the West today this is something they never saw and never experienced. 100% of the movie star parents opposing vaccines never knew the fear these diseases created. They are by any measure totally and supremely ignorant. 100 years ago more then half of children died before the age of 5 from (mostly) childhood diseases that we vaccinate for today. I see no logical reason to “require” vaccinations for children and then allow generous and easily exploited opt out options. The opt out should be eliminated, regardless of the reason and any parent not complying should have their child taken by the state (they do it if the child is obese!) and given the vaccinations.

    • Wrong says:

      Well, there is one opt out that needs to be kept in place: Medical. Some people aren’t capable of taking vaccines, be it because of an allergy to the components, being severely immunocompromised, or in the case of Whooping Cough, not being old enough for the vaccine. That’s the only opt out that really matters, especially since these people are forced to depend on herd immunity.

    • Janet Camp says:

      Where and when was a child removed by the state for obesity? I agreed with you up to that point, but while I am aware of efforts to make parents accountable for a child’s weight, I cannot imagine the child actually being removed from the parent–no wait, I think there was an extreme case of hideously, morbidly obese children I saw on Oprah once where they were removed–maybe. But even if this is true, surely it is rare and would hardly be a great example a way to deal with vaccines. Such a policy would only lead to lawsuits and recriminations. There SHOULD, however, be a lot more public education, including massive Public Service Announcement ads on TV and internet.

      Just to be clear, the only time I’ve seen Oprah is when I am trapped somewhere that has is on, such as an office or a family situation. I don’t personally own a TV.

    • Mario says:

      The sad part is that most of the people, even in front of the facts, just doesn’t realize the importance of vaccines and other proven medical treatments, as an example the introduction of the pneumococcus and rotavirus vaccines in my country, made the diseases caused by those infectious agents take a dive in the statistics of the primary health care units, but in less than 4 years of the new vaccines we are facing with people missing doses on the account of myths and lack of fear for the diseases that until recently killed thousands of children every year, even when those vaccines are free of charge and that’s without an antivaccine movement talking crazy on the TV.

  5. When I was a kid my mother deliberately infected me with all the childhood diseases. Vaccination wasn’t available. Whooping cough is truely no fun at all. Neither is measles or mumps.Also polio victims were a reasonably common sight. It helped. My kid was vaccinated. But the number of parents familiar with the diseases has declined so fewer are in favour of vaccination.

  6. BillG says:

    Steven, perhaps some of the pseudo skepticism from the anti-vaxers is the reaction that the medical establishment has over prescribed meds, occasionally for bogus like conditions. Depression is a disability and should not be taken lightly, but not for 10% of society. Hyperactivity, restless leg syndrome, acid reflux: can we not ditch the drugs, alter our lifestyle on many of these conditions?

    This spill over may have parents questioning the complicity of doctors and drug companies cash motives, though at a steeper cost to their children. If we cry wolf on every condition, perhaps vital necessities (vaccines) get dismissed or are called questionable.

    • Janet Camp says:

      You make broad and unsupported assumptions about “hyperactivity” (I assume you mean ADHD), for one. Parents who question a medical diagnosis of ADHD or its treatment are as biased and uninformed as the anti-vax people. Just because you have heard that this condition is “crying wolf” or “questionable” doesn’t make it so. Such a presumption reminds me of the same kind of reasoning that parents use when they opt for the “alternative” vax schedule.

      Much the same for your ideas on depression–which is more common than you might think. I’d have to research the actual numbers, but that’s beside the point, which is that you just assume that 10% is not plausible. I have no idea how common restless leg syndrome is, and it may or may not be over-hyped, but again the problem is drug advertising, not whether or not doctors are mis or over diagnosing it.

      It is exactly this kind of thinking that causes parents not to vaccinate and to question the science and the doctors who practice SBM.

    • I’d question your saying that depression is “overprescribed,” too.

    • tmac57 says:

      Well,I guess that I’m going to have to chime in with an objection about including acid reflux too.Acid reflux
      (GERD ) cannot always be successfully treated with diet,and GERD is the main cause of Barret’s esophagus,and esophageal cancer.It is indeed,a condition to take seriously,and modern medications such as PPI’s,are,for lack of a better expression,a ‘godsend’,for people that suffer from GERD.

      • tmac57 says:

        Oops,that should have read:”GERD is the main cause of Barret’s esophagus,which can cause esophageal cancer.”

  7. Max says:

    “Often anti-vaxers point out that when such outbreaks occur it is common for most infected individuals to be among the vaccinated. They imply that vaccines therefore do not work. This is also the case with the whooping cough outbreak. This is an abuse of statistics, however.”

    Right, they read that 80% of whooping cough patients had been vaccinated, and conclude that the vaccine has an 80% failure rate.
    But you can get these stats with a vaccine that has a 20% failure rate.
    Say 100 people are exposed, 95% of them are vaccinated, 5% are not, the vaccine has a 20% failure rate, and all unvaccinated people get sick.
    Then 0.2*0.95*100 = 19 vaccinated people get sick, and 0.05*100 = 5 unvaccinated people get sick for a total of 24 patients, 80% of whom had been vaccinated.

    • Wesley Goodford says:

      Let ¬x = 1 – x, e.g. ¬x + xa = (1 – x(1 – a)) = ¬(x¬a)
      ¬x = y implies x = ¬y
      ¬0 = 1 = 100%

      f = failure rate
      p = fraction sick among unvaccinated and vaccinated but failed
      v = vaccination rate

      us = ¬v p = fraction unvaccinated sick
      vs = v f p = fraction vaccinated sick

      s = us + vs = fraction sick total
      = p(¬v + v f)
      = p¬(v¬f)

      sv = vs / s = % sick people vaccinated
      = v f / ¬(v¬f)
      = ((v f)⁻¹ – f⁻¹ + 1)⁻¹
      = (1 – (1 – v⁻¹) / f)⁻¹
      = (¬(¬v⁻¹ / f))⁻¹
      (independent of p)

      Your example: sv = (¬(¬95%⁻¹ / 20%))⁻¹
      = (¬(5¬20/19))⁻¹ = (¬-5/19)⁻¹ = 19/24 = 79%
      80% failure, 100% adoption: sv = (¬(¬100%⁻¹ / 80%))⁻¹ = 100% (obviously)
      80% failure, 95% adoption: sv = 94%

      sv > f as long as:
      ¬(¬v⁻¹ / f) < f⁻¹
      f – ¬v⁻¹ < 1
      -¬v⁻¹ < ¬f
      v⁻¹ (¬f + 1)⁻¹
      So for an 80% effective vaccine, the number of vaccinated people among the sick will always be bigger than the failure rate as long as:
      v > (80% + 1)⁻¹
      v > 56%
      To get an idea of edge-case behaviour:
      Lousy vaccine: (1% + 1)⁻¹ = 99% (if almost everyone gets sick, almost everyone must be vaccinated for the condition to hold)
      Good vaccine: (95% + 1)⁻¹ = 51% (fraction of vaccinated sick people will be bigger than the failure rate as long as they’re in a clear majority)
      The latter may be surprising, but remember that the failure rate is low in this case.
      Also check sv for f near 0:
      sv = (¬(¬v⁻¹ / f))⁻¹
      = (-¬v⁻¹ / f)⁻¹
      = f / -¬v⁻¹
      So when comparing sv to f, v sort of tips the scale, with balance point:
      -¬v⁻¹ = 1
      v = 50%

      As a final note, in practice p is a complicated function of v¬f and f is not necessarily a good model because vaccines often don’t fail completely.

      • Max says:

        Right, when half the population is vaccinated, the ratio of vaccinated patients to unvaccinated patients exactly equals the failure rate, and the ratio of vaccinated patients to all patients approximately equals the failure rate when the failure rate is small.

      • Wesley Goodford says:

        By the way, I got a typo in this line:
        v⁻¹ (¬f + 1)⁻¹
        That should be:
        v > (¬f + 1)⁻¹
        I don’t know how that happened; I got it right in the sample calculation.

      • Kenneth Polit says:

        Hey, I read this post under the assumption there would be no math.

  8. Ken says:

    The success is part of the problem. The current generation of parents were themselves vaccinated, so haven’t seen firsthand what polio, measles, and so forth can do. So they don’t really understand the point of vaccination, in the way that their own parents do – see CountryGirl’s note.

    I suppose one solution would be to let immunization rates fall enough to have another generation of epidemics, but that seems both harsh and stupid.

  9. Max says:

    Vaccines like MMR have reduced the risk of diseases like measles to the point where the cost of vaccination almost exceeds the short-term benefit for an individual.

    This results in a variant of the Volunteer’s Dilemma.

    “A group needs a few volunteers, but each member is better off if others volunteer… A particularly vexing manifestation of this game occurs when a vaccination known to have serious risks is needed to prevent the outbreak of a fatal disease. If enough of her neighbors get the vaccine, each person may be protected without assuming the risks.”

    Freeriding might work if anti-vaxxers were uniformly distributed and surrounded by vaccinated people, but as Steve pointed out, they form clusters raising their risk.

    • Wesley Goodford says:

      In most civilised countries the vaccines used are too safe for this to matter. Still, the volunteer’s dilemma crops up in other places and it’s one of the many reasons we live together in a society with laws and a police force.
      Note that since there is no real difference between action and inaction the volunteer’s dilemma is identical to the tragedy of the commons. Both are of the form ‘every individual is better off making choice A but society is better off if at least some individuals make choice B’.

      • Max says:

        Moreover, as Steve said, herd immunity requires many volunteers. But “Do it for the herd” is a harder sell than “Do it for your children.”

      • Chris says:

        It was also tried, and failed in Japan:
        Measles vaccine coverage and factors related to uncompleted vaccination among 18-month-old and 36-month-old children in Kyoto, Japan

        Since measles is so communicable, you need at least 95% coverage for herd immunity to actually work. This is what happened:

        According to an infectious disease surveillance (2000), total measles cases were estimated to be from 180,000 to 210,000, and total deaths were estimated to be 88 [11,12]. Measles cases are most frequently observed among non-immunized children, particularly between 12 to 24 months. However, a nation-wide survey conducted in 2000 showed that measles vaccine coverage in Japan was 81.4%, which is not enough to prevent outbreaks [13].

  10. d brown says:

    One point. Almost all polio in America is from the newer live vaccine used. If given the first killed vaccine nobody gets polio. Back in the old days it was decided to use live vaccine so that kids would pass some immunity to others. It may have worked as a public health measure then. But that time is past. It costs more for the killed vaccine, but your kid will never ever get polio. Whats best for most is not always best for one. I am 65 years old. The Army said my IQ was 128 or so. I could never use it to do anything in today’s world, at least without money. The VA says I have some kind of ADHD. My life would have been very different if it had been know and something could have been done besides telling me I would not work hard.

    • Wesley Goodford says:

      The last case of naturally occurring polio in the US was in 1979. About 1 in 750 000 people administered with the OPV vaccine gets polio; the last case was in 1998, except for a small outbreak in 2005, also traced to the OPV vaccine, which was discontinued in 2000.
      In that instance, 1 immunodeficient patient died. There were concerns about some other people getting infected, but the statistics only mention 1 patient so I assume they’re well.
      P.S. If you have ADHD or something similar, it’s a good idea to re-read your comment before posting it to check if you stray off-topic.

  11. DeLong says:

    I am in my 60’s+ and was a child before most vaccines were developed. The only vaccines I clearly received were for polio and smallpox. I clearly remember having measles, mumps and chicken pox as a child. If my memory serves me correctly, I was really sick with mumps on a summer day and watched through the window as all of my friends played in MY front yard! Since then, I’ve made sure that I have received every vaccination medical science recommends for me, as well as for my wife and child. The benefits far out weigh the risks. What is really odd about the anti-vaccine movement is that several people I know that deny their children vaccines will not hesitate a moment to ask their doctor for an antibiotic for a viral infection! Also, most of these people readily accept other prescription drugs (as well as OTC drugs)! The sad thing about this is that innocent children are the victims of their parent’s ignorance.

  12. CountryGirl says:

    The problem with ADHD is that no one can diagnose it with certainty and far too many people without the proper training have diagnosed children as ADHD arbitrarily. It is common for teachers to make the diagnosis and recommend treatment and it is common for doctors to simply accept the “referral” without question. It is quite probable that what we commonly think is ADHD is in fact normal and in fact a trait that worked to an advantage in a hunter gatherer society. Most ADHD is nothing more then young boys not adjusting to sitting in a classroom for 7 hours. I do sympathize with the teachers who have to deal with 25 children for 7 hours a day but that’s the job they choose.

  13. d brown says:

    Posting some place like this gets you updated fast. “have ADHD” The point is that it is real. No matter if there are misdiagnosis

    • CountryGirl says:

      You may have ADHD (if it is real) or you may simply be a variation of “normal”. What makes you believe you have ADHD? Do you read books, watch movies, work 8 hours a day? Maybe you have been misdiagnosed. If you were and if you were prescribed medicine then you were put at risk needlessly. If that turns out to be true can you still say “No matter if there are misdiagnosis”? If a misdiagnoses results in risky medication does it matter?

      • d brown says:

        I was asked for this. ADHD is hot here. As for me I had a Army GA score of 126 (was going into old files not long ago.) 140, 130s but with some 50’s. I read all the time and after I was given a WP in my mid 50’s I love to write. Never could before at all! No mind testing in the early 60’s. What good would it do now. I’ve read that moms want their kids to test that they have ADHD to get easier testing on grades. Sounds a lot like R/W BS. A few maybe, but enough to matter? ADHD seems to be a general name for somethings that are not understood.

      • d brown says:

        Err, I’d like to stop taking up space here about me and ADHD. Something makes some peoples brains just not get trackshion on the things most needed in today’s world. Like Bush 1? Call it what you will. Most people in jail are dim. But some are well above average in IQ. I have read that their brains do not put them where there their IQ should, and they know it. So they do smart crimes to get the good stuff others have. A lot of waste is going on.

  14. Kenneth Polit says:

    I don’t understand the anti vaxx movement at all. Jeebus people, just get the frakking shots and knock this crap off. When an anitvaxxer is lowering her child’s coffin into the earth is it in bad taste to say, “At least he didn’t get autism.”?

    • Kenneth Polit says:

      Sorry about that, but I have little sympathy for stupid.

    • Chris says:

      Oh, you’ll love one of the newest reasons to not protect kids against chicken pox: children getting chicken pox helps prevent adults getting shingles.

      There is some truth in that, but it is silly when there is a vaccine for shingles (which essentially does the same thing as hanging around a kid who has chicken pox). I personally think it is cruel to make a kid spend up to two weeks covered in itchy painful pox just because an adult does not want a shingles vaccine.

      And I know the varicella vaccine is not perfect, a child may still get chicken pox. But it will be milder and not last as long. Since we had a full month of chicken pox in our house before there was a vaccine, I see no reason to let kids suffer like mine did. A milder version is much much better than full blown chicken pox.

  15. d brown says:

    Like the R/W the anti vaxx movement thinks someone, somewhere is out to get them.